Optical Spring Effect Research Articles

Experimental evidence for an optical spring

An optical spring effect has been observed in the motion of a Fabry-Perot cavity suspended in the Low-Frequency Facility, R and D experiment of the VIRGO Collaboration. The experimental setup consists of a 1-cm-long cavity hanging from a mechanical isolation system, conceived to suppress seismic noise transmission to the optical components of the interferometer. The observed radiation pressure effect corresponds to an optical stiffness k{sub opt} ranging between 2.5x10{sup 4} and 6.5x10{sup 4} N/m. This paper reports several measurements of the mirror relative displacement carried out in different working conditions. The measured error signal spectra show broad resonances at frequencies compatible with the optomechanical system. In other runs cavity detuning oscillations have been observed at subhertz frequencies. In these cases the power spectrum of the control loop error signal exhibited a broad resonance with superimposed uniformly spaced peaks. These observations, validated by a simple model, prove that the fluctuations of the optical spring effect can become so large as to exhibit nonlinear features.

Observation and characterization of an optical spring

Recent theoretical developments have highlighted the potential importance of ``optical springs'' in interferometers for gravitational wave detection as a means for beating the standard quantum limit. We have observed an optical spring effect experimentally in a detuned Fabry-Perot resonator in which one mirror is mounted on a flexure so that it has a significant response to radiation pressure. The main effect of the optical spring, an observed shift in the mechanical resonance frequency of the moveable mirror, agrees well with a simple model.

An experiment to investigate optical spring parametric instability

Recently it has been shown that parametric instabilities may significantly affect the performance of high power signal recycling gravitational wave interferometers such as the planned Advanced LIGO. We propose an experiment utilizing the optical spring effect to determine the likelihood of parametric instability. A mechanical resonator has been designed to maximize parametric instability with R0 = 500. We show that cold damping will reduce the quality factor to ∼1000 while the rigidity is increased to ∼1500 N m−1.